Friday, October 12, 2007

Tigers Offense Sabermetrically Correct in 2007

This year, many fans complained that the Tigers left too many runners on base and did not get the most out of their offense. They said the same thing about last year's team, especially in the second half. However, I found that they got more out of their hits, walks and various other positive batting events than any other team in the league in 2006.Today' I'm going to look at 2007.

The Tigers finished second in the league with 887 runs scored in 2007. Should the Tigers have scored more runs from their offensive output? One way to answer this question is to look at runs created (RC). RC is calculated from the number of walks, singles, doubles, triples, homeruns and other things that a team does to score runs. Bill James showed in his Baseball Abstracts many years ago that RC is highly correlated with runs scored. This tells us that runs scored are essentially the sum of other team statistics and are not, in general, accounted for by unmeasured factors. There are many RC formulas but they all have the same basic structure:

RC= (A*B)/C

where A=number of runners on base, B=advancement of runners and C=the opportunities to do A and B.

One of the first runs created formulas was invented by Bill James in 1979. It was simply:

RC=((hits+walks)*total bases)/(ab+walks).

This version is still useful for some purposes but the formula has evolved over the years and more recent versions are more accurate in estimating runs scored.Sabermetrician Dan Fox gave a brief history of runs created on his blog.The formula I am using here is:

This looks really complex but it does not give hugely different results from the earlier more simple formulas. So if you want to tune out this version of formula and just think of the (A*B)/C thing, you should be OK.Table 1 lists the runs, RC, difference between runs and RC and % difference for all American League teams in 2007.Table 2 does the same for National League teams.The first thing you should notice is that all but 3 teams had RC estimates within 5% of their actual runs scored.This means that runs created gives a good estimation of runs scored in most cases.

A closer look at table 1 shows that the Tigers had 891 runs created in 2007.This is just 4 runs more than their actual runs scored total. Thus they scored almost as exactly as many runs as they would have been expected given their offensive output. In 2006, they scored 16 (or 2%) more runs than their runs created which was better than any team in the league. They weren't as efficient (lucky?) this year but they were not inefficient either.

The team which got the biggest bang out of their offensive output was the Texas Rangers who scored 47 (or 6%) more runs than their RC estimate. The least efficient team was the Tampa Bay Rays who scored 30 (3.6%) runs fewer than their RC.

In the National League, only the San Diego Padres scored more runs (and only 2 more runs at that) than they created. The least efficient or unluckiest team in the National League was the Florida Marlins who scored 56 (or 6.6%) fewer runs than their RC estimate.